Method of assembling a chromatography column

ABSTRACT

Disclosed is a method of assembling a chromatography column including the steps of providing a cylindrical core element, winding an innermost layer of uniformly spaced fibers helically about the core element, winding a plurality of concentric annular layers of uniformly spaced fibers about the innermost layer so that the fibers of each layer are helically wound about the most inwardly adjacent layer in reverse hand orientation relative to the next inwardly adjacent layer, enveloping the outermost layer of fibers in a column housing, and coating the fibers with stationary phase material.

This application is a division of application Ser. No. 07/041,554, filed4/22/87 now U.S. Pat. No. 4,872,979.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to chromatography and more particularly tochromatographic columns having particular utility in preparative gaschromatography.

Previously, there have been essentially two formats of gaschromatographic columns. The more efficient format is that of an opentubular column with the walls coated with the stationary or fixed phasematerial. This format, sometimes referred to as a Golay or capillarycolumn, is used for chemical analysis in which small samples aresufficient.

When the output of a capillary column is not sufficient for the desiredanalysis or when larger outputs are required for further chemicalprocesses as in preparative scale chromatography, the preferred formathas been that of a tube packed with porous particles or granulesimpregnated or coated with the fixed phase material. This format,generally referred to as a packed column, has the advantage ofrelatively large throughput, but is slower and less efficient.Typically, with equal pressures being applied at the inlet of thecolumns, a separation requiring one minute with a capillary column willrequire several hours with a packed column.

The poor efficiency of the packed column is explainable by certainnonuniformity characteristics of this format. Firstly, there is thecircumstance that any one rivulet of gas snaking its way among thepacking granules alternately encounters very narrow passages betweenthree contacting granules which offer high resistance to flow and largepassages which require relatively long times for the sample molecules todiffuse to and from the fixed phase which is coated on the walls ofthese larger passages. In contrast, the single passage of a capillarycolumn is of uniform dimension and this single dimension determines boththe resistance to flow and the diffusion time to and from the wall.Secondly, there is the circumstance that the various rivulets of gaswhich may have a common origin and which meet again further along thecolumn may have required appreciably different times for their separatetravels. These travel time differences cause an unwanted spread of thevarious separated components in space along the column and eventually intime at the column exit and consequently the components may merge intoeach other instead of being clearly separated. Thus, there are someundesirable attributes of lengthwise and crosswise nonuniformity of thecolumn.

From time to time there have been suggestions to provide a column ofhigher throughput and high time-wise efficiency by manifolding a numberof like capillary working in parallel as a single column. However, thissuggestion has not been successful. Firstly, such a column would be costprohibitive, e.g., the cost of one hundred capillary columns would beprohibitive. Secondly, the task of trimming such a large number ofcolumns so that they would have the same time of passage for all thecomponents of a given sample would be practically hopeless.

Accordingly, it is an object of the present invention to provide a newand improved chromatographic column.

Another object of the invention is to provide a chromatographic columnhaving high efficiency and relatively large throughput suitable forpreparative scale chromatography.

A further object of the invention is to provide a chromatographic columnhaving multiple uniform passageways with crosswise communication forattaining uniform frontal distribution of separated components. Includedin this objective is the provision of passageways having a high degreeof lengthwise and crosswise uniformity.

A still further object of the invention is to provide such achromatographic column which is economical to manufacture and efficientin operation.

A still further object of the invention is to provide a new and improvedtechnique for forming a chromatographic column which is economical andefficient.

Other objects will be in part obvious and will be in part pointed outmore in detail hereinafter.

Accordingly, it has been found that the foregoing and related objectivesand advantages can be obtained in a chromatographic column comprising ahousing having an inlet and an outlet end and a plurality of uniformfluid passageways extending axially within the housing between the inletand outlet ends. The passageways are coated with a stationary phasematerial and lateral openings disposed longitudinally along thepassageways laterally interconnect adjacent passageways to permit fluidcommunication and/Or molecular diffusion therebetween. In a preferredembodiment of the invention, the plurality of the fluid passageways areformed by a configuration of fiber layers disposed about an elongatedcentral core element extending longitudinally within the housing. Thefiber layer configuration comprises an innermost layer having aplurality of fibers helically wound about the central element with thefibers being in predetermined spaced disposition for forming a fluidpassageway between adjacent fibers. A plurality of outwardly successivefiber layers are disposed about the innermost layer with each successivelayer having a plurality of fibers helically wound in reverse handrelative to the previous adjacent layer and in predetermined spacedisposition for forming a fluid passageway between adjacent fibers witha plurality of lateral openings fluidly cross-connecting overlappinglongitudinal fluid passageways.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly broken away perspective view of a chromatographiccolumn according to the present invention.

FIG. 1A illustrates an end view of a fiber of a layer with thestationary phase material coated thereon.

FIG. 2 is a cross-sectional view of an alternate fiber element.

FIG. 3 is a cross-sectional view of another alternate fiber element.

FIG. 4 is a schematic diagram of a gas chromatography system includingthe column of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although specific forms of the present invention have been selected forillustration in the drawings, and the following description is drawn inspecific terms for the purpose of describing these forms of theinvention, the description is not intended to limit the scope of theinvention which is defined in the appended claims.

Referring to FIG. 1, the chromatography column of the present inventionis designated by the numeral 10 and generally comprises an elongatedcolumn housing 11, an elongated central core element 12, a configurationof fibers, generally designated by the numeral 14, disposed about thecore element 12 so as to form a plurality of fluid passageways throughthe housing 11, and a coating 13 of stationary phase material on thepassageways.

The core element 12 is a cylindrical fiber extending coaxially withinthe cylindrical housing 10 between the inlet end 16 and outlet end 17 ofthe housing. The fiber configuration 14 comprises a plurality ofannular, concentric, wound fiber layers 18, 20, 22, 24 extending betweenthe core fiber 12 and the inner wall 26 of the cylindrical housing 11.

The innermost fiber layer 18 is formed by a plurality of uniformlyspaced cylindrical fibers 28 helically wound about the core fiber 12.The spaces 30 between the fibers 28 form uniform parallel fluidpassageways being bound on the inner side by the core element 12 and onthe opposing outer side by the adjacent fiber layer 20. The fiber layer20 is similarly formed by a plurality of uniformly spaced cylindricalfibers 32 helically wound about the innermost layer 18 in reverse handrelative to the fibers 28 of layer 18. The spaces 34 between adjacentfibers 32 form parallel uniform passageways bound on the inner side bythe next innermost adjoining layer 18 and bound on the outer side by thenext outermost adjoining layer 22.

In the illustrated embodiment, the helically wound fibers 28 of theinnermost layer 18 are right hand wound so that the passageways 30follow identical right hand helical paths about the core fiber 12between the inlet end 16 and the outlet end 17 of the housing 11.Conversely, the passageways 34 formed by the left hand helically woundfibers 32 follow a left hand helical path about the inner layer 18between the inlet and outlet ends of the housing 11. Consequently, theleft hand oriented passageways 34 cross over the right hand orientedpassageways 30 so that common uniform lateral openings 36 are formedbetween the passageways 30, 34 where the passageways 34 adjoin thepassageways 30 to thereby fluidly interconnect the overlapping fluidpassageways at a plurality of locations longitudinally along thepassageways.

Similarly, the fibers 38 of layer 22 are uniformly spaced and helicallywound in right hand orientation about the layer 20. The spaces 40between the fibers 38 form uniform fluid passageways being bound on oneside by the next inwardly adjacent fiber layer 20 and being bound on theopposite side by the next outwardly adjacent fiber layer 24. Thepassageways 40 follow a right hand oriented helical path about the layer20 and therefore crossover the left hand helical passageways 34 of layer20. Common uniform lateral openings 42 are formed between thepassageways 40, 34 where the passageways 40 adjoin the passageways 34 tothereby fluidly interconnect the overlapping passageways longitudinallyalong the passageways between the inlet and outlet ends of the housing.

The outermost fiber layer 24 is similarly formed by a plurality ofuniformly spaced cylindrical fibers 44 helically wound in left handorientation about the fiber layer 22. The spaces 46 between the fibers44 form passageways bounded on the outer side by the inner wall 26 ofhousing 10 and on the inner side by the fiber layer 22. The housing 11is in close fitting disposition about the annular layer 24.

The left hand helical passageways 46 of layer 24 cross over the righthand helical passageways 40 of layer 22 so that common uniform lateralopenings 48 are formed between the passageways 46, 40 where thepassageways 46 adjoin the passageways 40 to thereby fluidly and/ordiffusively interconnect the overlapping fluid passageways at aplurality of locations longitudinally along the passageways. Overall,the uniform lateral openings disposed longitudinally along the column 10provide for cross-communication or crossdiffusion of carrier gas andsample for equilibrium between the passageways for the entire column.

The fibers 28, 32, 38, 44 are of equal diametrical size being typically0.008 inch diameter titanium wire. The core fiber 12 has a diametricalsize typically 5 times the size of the other fibers, being thusapproximately 0.04 inch diameter titanium wire. Alternately, a coreelement of another dimension may be used, such as a fiber similar tothose used in the fiber layers.

In the typical configuration shown, the innermost layer 18 has 9 fibersand each radially outwardly successive fiber layer increases by threefibers, i.e., fiber layer 20 has 12 fibers, fiber layer 22 has 15fibers, and fiber layer 24 has 18 fibers. As can be appreciated, thenumber of uniform passageways formed by each fiber layer is equal to thenumber of fibers in the respective layer.

The fibers 32, 38 of the intermediate layers 20, 22 are equi-spaced byapproximately their diametrical size, i.e., 0.008 inches. The climbingangles of the helically wound fibers of the intermediate layers 20, 22are equal being approximately 20°. Since the fluid velocity through thepassageways 46 of the outermost layer 24 is slowed by the influence ofthe adjacent inner wall 26 of housing 11, the climbing angle of thisoutermost layer is steeper so that the distance between the adjacentfibers 44 is greater than the diameter of the fibers; also, the pathlengths along this outer layer will also be shorter than the neighboringinner layer, all for the purpose of attaining uniform frontaldistribution of the sample elements. A similar compensation is likewiserequired for the innermost layer 18 because of the influence of theadjoining core fiber 12, i.e., a steeper climbing angle. In theillustrated embodiment, the climbing angles of the fibers 28 and 44 are10°.

Although only two intermediate fiber layers 20, 22 have been shown inthe illustrated embodiment, it is understood that any suitable pluralityof such intermediate layers may be utilized depending upon the outputdesired with the fibers of each successive fiber layer being helicallywound in reverse hand relative to the next adjacent layer and with theintermediate layers having equal climbing angles.

The cylindrical housing 11 closely envelopes the outermost fiber layerand withstands the input pressure of the conventional chromatographicprocess. A suitable housing can be formed of TEFLON and heat shrunk byconventional methods to frictionally retain the fibers in the woundfiber configuration.

The passageways 30, 34, 40, 46 formed by the respective fibers 28, 32,38, 44 are coated with a conventional stationary phase material such asCARBOWAX. For purposes of explanation, FIG. 1A shows only one of thefibers 44 of layer 24 with the coating 13 thereon. Such coating isaccomplished by coating the fibers prior to assembly or, alternately,after assembly.

Titanium wire is the preferred material for the fiber elements althoughother metal wires such as aluminum provide acceptable results.Alternately, the fibers may be made of glass or glass-like substancessuch as fused silica.

Alternate fiber forms may be utilized for the wound fiber layers. Asquare fiber 50, such as shown in cross-section in FIG. 2, may beutilized as well as a fiber 52 being quadrilateral in cross-section witha pair of opposed incurvated sides as shown in FIG. 3. The intendedadvantage of the quadrilateral configuration is to avoid narrow cornersthat would constitute a stream holdup.

In operation, the column 10 of the present invention is utilized in aconventional system which is schematically illustrated in FIG. 4 andneed not be described in great detail. As shown in FIG. 4, the inlet end16 of the column is connected to the sample introduction system 54. Asource of carrier gas 56 is interconnected to the sample introductionsystem 54 by a flow control regulator 58. A conventional detector 60 isconnected to the outlet end 17 of the column 10.

The method of forming or assembling the column of the present inventionincludes maintaining the core element in a linear disposition andhelically winding a plurality of wire elements about the core element inuniform predetermined spaced disposition at a predetermined climbingangle as previously explained. A second layer is formed by helicallywinding a plurality of fiber elements in opposite hand about the firstlayer in predetermined spaced disposition and at a predeterminedclimbing angle as previously explained. Successive fiber layers aresimilarly formed each being wound in reverse hand relative to theprevious adjacent layer. When the desired number of layers have beenappropriately wound, the column housing is mounted about the fiberconfiguration. The housing is formed of TEFLON and heat shrunk byconventional methods to frictionally retain the fiber configuration. Thepassageways formed by the fiber layers are coated with a stationaryphase material by coating the fiber elements defining the passageways.The fiber elements are coated prior to winding or, alternately, afterwinding.

As can be seen, a chromatographic column is provided which achieves ahigh degree of lengthwise and crosswise uniformity as well as crosswisediffusion for attaining uniform frontal distribution of all componentsof a sample. The column has high efficiency and relatively largethroughput suitable for preparative scale chromatography and iseconomical to manufacture and efficient in operation.

As will be apparent to persons skilled in the art, various modificationsand adaptations of the structure and method above described will becomereadily apparent without departure from the spirit and scope of theinvention, the scope of which is defined in the appended claims.

I claim:
 1. A method of assembling a chromatography column comprisingthe steps of; providing a cylindrical core element, forming plurallayers of fibers onto said core element, each of said layers havingplural fluid passageways, each of said passageways is defined by a spaceexisting between every two adjacent fibers, wherein the step of formingthe layers comprises,winding an innermost layer of uniformly spacedfibers helically about the core element, winding a plurality ofconcentric annular layers of uniformly spaced fibers about the innermostlayer so that the fibers of each layer are helically wound about thenext inwardly adjacent layer in reverse hand orientation relative to thenext inwardly adjacent layer, enveloping the outermost layer of fibersin a column housing, and coating the fibers with stationary phasematerial.
 2. The method of claim 1 including performing the coating stepafter the step of winding a plurality of concentric annular layers. 3.The method of claim 1 including performing the coating step prior to thestep of winding a plurality of concentric layers.
 4. The method of claim1 wherein the windings of fibers form a fiber configuration and the stepof enveloping the outermost layer of fibers comprises mounting the fiberconfiguration in a close-fitting housing thereby frictionally retainingthe fiber configuration.
 5. The method of claim 1 including the step ofwinding the fibers of the intermediate layers between the innermost andoutermost layers at equal climbing angles.
 6. The method of claim 5including the step of winding the fibers of the outermost layer at asteeper climbing angle than the climbing angle at which the intermediatelayers are wound.
 7. The method of claim 5 including the step of windingthe fibers of the innermost layer at a steeper climbing angle than theclimbing angle at which the intermediate layers are wound.
 8. The methodof claim 1 including the step of winding the fibers of the intermediatelayers between the innermost and outermost layers to be equi-spaced afirst predetermined distance.
 9. The method of claim 8 including thestep of winding the fibers of the outermost layer to be equi-spaced asecond predetermined distance greater than said first predetermineddistance.
 10. The method of claim 8 including the step of winding thefibers of the innermost layer to be equi-spaced a second predetermineddistance greater than said first predetermined distance.